In this study of three great female primatologists, science journalist Montgomery moves beyond biography into ethology, taking a step that goes well beyond even her subjects' research. Goodall, Fossey and Galdikas each made a similar leap, the author contends, moving from observers and recorders to an almost shamanistic quest to enter the world of the apes they studied. These personal transformations are sketchily supported with anecdotes from the field, personal interviews and even a jarring account of an attempt to contact Fossey, after her death, via channeling. Montgomery adds little to Farley Mowat's 1988 biography of Fossey, Woman in the Mists , but she offers a few fresh angles on Goodall, Galdikas and other characters, human and ape, met before in their books. In an epilogue, Montgomery offers the intriguing view of these scientists as pioneers of a particularly female way of scientific knowing that deserves fuller argument than three portraits allow. Photos. (Mar.)